Coke ovens are used to produce coke from charcoal in iron and steel industry. They are constituted by alternatively disposing coking chambers and combustion chambers separated by oven walls made of bricks. A coking chamber has a parallelepiped shape, usually between 3.5 and 8 meters high, between 12 and 20 meters deep along a horizontal direction, and between 0.35 and 0.7 meter wide. They usually comprise two opposite doors respectively at both ends along the horizontal direction.
The coking process involves carbonization of coal to high temperatures, above 1000° C., in an oxygen deficient atmosphere in order to concentrate the carbon. Coal is charged from a coal charging hole at a top portion of the coking chamber. Then, a high temperature of 1000° C. or more is applied to the coal inside the coking chamber for approximately 20 hours. Coal is thereby coked (carbonized), and coke cake (hereinafter, referred to as just “coke”) is produced. When the coke is produced, doors disposed at both ends of the coking chamber are opened, the coke is pushed by a pusher from a lateral side of the coking chamber, and the coke is taken out of the coking chamber.
Apart from high temperatures, the coking process also generates a lot of dust, soot and steam.
When coal is transformed into coke, it exerts a high pressure onto the bricks of the oven wall which can then be deformed. These deformations of the oven walls may induce issues for pushing the coke out of the chamber and then increase damages of the oven walls. Moreover, the bricks are exposed to high temperature variations between oven loading and unloading and thermal shocks may occur, which also causes damages to the walls.
All these damages eventually alter the shape of the walls and impact the productivity of the coking plant by inducing issues during coal charging or coke pushing.
Measurements of the wall shape are performed after unloading and before the following loading. The wall temperature is typically in a 900° C. to 1000° C. range.
For this reason, there has been a need for monitoring the conditions of coke ovens, in particular in order to check whether the walls shape is not altered.
In the past, this was performed through visual inspection, but it involved a lot of safety risks for operators and was not very accurate.
Document JP2014-218557 describes using a 3D laser to assess the shape of the chamber wall. The laser is placed on a first location in front of a first door of the coking chamber so as to scan a portion of the left wall of the chamber. Then it is moved to a second location so as to scan a portion of the right wall of the chamber.
Besides, 3D laser scanners have been used in some other technical fields in order to measure three dimensional shapes. However, such scanners have been considered unfit for use within a coking plant, because they cannot withstand the hot, dusty and humid environment nearby running coke ovens.